1. Field of the Invention
The invention is directed to an improved fuel injection system and a pressure booster for an internal combustion engine.
2. Description of the Prior Art
German Patent Application DE 199 10 970, discloses fuel injection systems and pressure boosters in which a pressure booster, by means of filling and evacuation of a rear chamber, makes it possible to increase the fuel injection pressure beyond the value furnished by a common rail system.
German Patent Disclosure DE 31 02 697 describes a fuel injection system with a pressure booster whose rear chamber is in constant communication with a low-pressure line.
The fuel injection system and the pressure booster of the invention have the advantage over the prior art that because the high-pressure chamber of the pressure booster can be filled via the rear chamber, a separate bore serving solely to fill the high-pressure chamber need not be provided in a metal body of the pressure booster that leads the larger-diameter end of the pressure booster. Space is accordingly saved, which when the pressure booster is used in conjunction with injection system and the pressure booster defined by the independent claims are possible.
Integrating a throttle and/or a fill valve into the piston of the pressure booster is especially advantageous, so that for filling the rear chamber as well, no lines have to be led past the larger-diameter end of the piston any longer. The result is an even more-compact structure of the fuel injection system and the pressure booster.
If moreover the connecting line between the rear chamber and the high-pressure chamber and optionally also a check valve disposed in the connecting line are integrated with the piston of the pressure booster, a very slender, compact structure is obtained, which is ideal for installation in modern engines.
It also proves to be advantageous for the piston of the pressure booster to be composed of two parts of different diameters, which are movable relative to one another and thus, because of their movability relative to one another, they can perform not only the compressor function, but also the function of a valve, in particular a check valve. As a result, additional components for the provision of a separate valve assembly are eliminated, making further space-saving possible.
In further advantageous embodiments, the two-part piston takes on the function not only of a check valve but also of a fill valve, without requiring additional components for that purpose.